The general goal of this project is to delineate the mechanisms involved in antigen recognition by and activation of thymus-independent (B) and thymus-dependent (T) lymphocytes. Our approaches to the study of B lymphocyte function include: a) Evaluation of the immune response of CBA/N mice, which possess an X-linked immune defect in B cell function; b) The testing of conclusions reached from studies of CBA/N mice by study of inhibition of B cell responses of normal strains with antisera to B cell differentiation antigens and to immunoglobulin D allotypes; c) The evaluation of activation requirements of B lymphocytes through the use of anti-immunoglobulin. In the study of T lymphocytes, our general goals include attempts to develop systems which allow an evaluation of the contribution of histocompatibility antigens and of VH gene products to the recognition and activation processes. BIBLIOGRAPHIC REFERENCES: Ahmed, A., Scher, I., Sharrow, S.O., Smith, A., Paul, W.E., Sachs, D.H. and Sell, K.W.: B lymphocyte heterogeneity: Development and characterization of an alloantiserum which distinguishes B-lymphocyte differentiation alloantigens. J. Exp. Med. 145: 101, 1977. Paul, W.E., Shevach, E.M., Pickeral, S., Thomas, D.W. and Rosenthal, A.S.: Independent population of primed F1 guinea pig T lymphocytes respond to antigen-pulsed peritoneal exudate cells. J. Exp. Med. 145: 618, 1977.